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Genetic screening results don’t influence most mothers’ decisions to have another baby, according to a new study.

Researcher and lead author of a new study, Yvonne Bombard, is also mom to a 2-month-old son, Rafael. Bombard's paper found that some mothers "make inappropriate use of the information" from their newborn's genetic screening. (Richard Lautens / Toronto Star) | Order this photo

A majority of mothers ignore their newborn’s genetic screening results when deciding whether to get pregnant again, a new Canadian study suggests.

The paper, published online Thursday in the journal Genetics in Medicine, questions the “reproductive benefits” of sharing certain genetic testing results with parents when “people don’t make use of the information or make inappropriate use of the information,” said Dr. Yvonne Bombard, a genomics health services researcher at St. Michael’s Hospital and lead author.

Newborn screening is widely considered a public health success story. Within two days of a baby’s birth, an infant’s heel is pricked for a blood sample, which, in Ontario, may be analyzed for 29 rare but treatable diseases. Early detection means early treatment, which has been credited with saving lives.

But the screening process doesn’t just zero in on sick infants. It also captures genetic mutations for various diseases that don’t actually affect the child.

The research, led by Dr. Fiona Miller, a health policy researcher at University of Toronto, and Dr. Robin Hayeems at SickKids, followed a group of mothers whose babies carried a genetic marker for cystic fibrosis, which generates a large number of carriers and causes problems with breathing and growth.

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Babies with cystic fibrosis have two copies of a mutation for the disease. Babies who are carriers for cystic fibrosis have just one copy of a mutation and generally do not require clinical treatment. The mutation will not cause the disease on its own because it’s recessive. But there are reproductive implications.

“It’s a very interesting policy and ethical issue that was raised when carrier status became identifiable through newborn screening,” Bombard said.

“There is no clinical use to learning that information for that child. But there is a reproductive benefit for their parents immediately. Should they choose to have more children, then it’s likely that one or both of them are carriers and therefore they would be at risk of having an affected child.”

Still, 65 per cent of the mothers in the study said they did not expect the screening results to influence their family planning. All the mothers said they valued learning their infants’ carrier results and a little more than half had carrier testing themselves. Others admitted they “told everyone” in their families that they may be cystic fibrosis carriers without confirming which side of the family was at risk. Bombard advises against this approach, warning it “may create more carrier testing and counselling services than would otherwise be necessary.”

The study also noted that some parents elected to have other children in the family tested, which Bombard also cautioned against.

“International guidelines recommend against carrier testing in children because there is no immediate clinical value to learning if a child is a carrier of a disease,” Bombard said. “Identifying carriers through newborn screening actually conflicts with international standards. It’s a consent issue.

“The argument is they should go out and get tested themselves when they can provide consent. It’s not of clinical value to them when they’re children because 6-year-olds aren’t about to have children. And if you never have the chance to say yea or nay as to whether you wanted it, that’s the issue.”

As with everything in science, there are benefits and risks to learning about carrier status.

“It might create undue anxiety and misunderstanding,” Bombard said. “Some parents might consider their child vulnerable or treat them differently . . . The thing with information is you can never unknow it.”

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